Currently, spin valves are conventionally used for the magnetoresistive (MR) element in MR heads. A spin valve includes two magnetic layers, a free layer and a pinned layer, a spacer layer, and a conventional antiferromagnetic (AFM) layer. The spin valve may also include a capping layer. The free layer and pinned layer are separated by the spacer layer. The magnetization of the pinned layer is typically fixed by exchange coupling to the conventional AFM layer.
A conventional MR head may include either a top spin valve or a bottom spin valve. A top spin valve is one in which the pinned layer and AFM layer are near the top of the spin valve, while the free layer is near the bottom of the spin valve, in proximity to the substrate. A bottom spin valve is one in which AFM layer and the pinned layer are near the bottom of the spin valve, while the free layer is near the top of the spin valve.
Typically, the conventional AFM layer in a top spin valve is formed of PtMn, PtPdMn, IrMn, NiMn, CrPtMn, RhMn, NiO, or NiCoO. If PtMn, PtPdMn, IrMn, NiMn, CrPtMn, or RhMn is used for the AFM layer in a bottom spin valve, the exchange coupling between the pinned layer and the conventional AFM layer is quite small. This reduces the magnetoresistance of the spin valve, lowering the signal provided by the MR head as well as the magnetic and thermal stability of the MR head. Consequently, the conventional AFM layer in a bottom spin valve is typically NiO or NiCoO. Bottom spin valves are more desirable than top spin valves for a variety of reasons. Accordingly, what is needed is a system and method for providing bottom and dual spin valves that can use an AFM layer other than NiO or CoO. Moreover, it would also be desirable to provide a bottom spin valve which uses a synthetic AFM layer. The present invention addresses such a need.